Ecostar out on trial
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by Colin Sowman • Ford is placing 80 of an initial batch of 105 electric-powered Ecostar Escort vans with customers for evaluation. Their top speed is limited to 112km/h (70mph) with a payload of 370kg, an average range of 150km (94 miles) and a recharging time of five to seven hours.
Electrical power comes from 480 sodium sulphur cells each producing around two volts. These are connected to produce 330 volts at 80 amps continuously (up to 50kW for short periods). This is converted to threephase alternating current for the motor which is rated at 75hp (56kW) and delivers 193Nm (1421bift) of torque.
Drive from the motor is taken through a 13.2:1 reduction gear set directly to the single-speed transaxle. When the vehicle is moving and the accelerator pedal released, the motor switches to a regenerative braking system. Pressing the brake pedal increases the amount of regeneration (and retardation) before the foundation brakes help out. The motor can turn around 25% of the kinetic energy back into electricity giving up to a 7% recharge of the batteries. Foundation brakes are discs at the front and drums at the rear.
Sodium/sulphur batteries produce up to three times the output of lead acid and have a working temperature of around 300'C. They are in a doubleskinned stainless steel container with the middle evacuated to retain the heat. Weighing 350kg, the battery pack contains both heating and cooling elements (which can maintain the temperature for five days) and is positioned beneath the floor ahead of the rear axle. The usual electric functions are powered from a 12V battery recharged from the traction batteries.
Offsetting the batteries' weight (apart from the removal of the drivetrain) are alloy wheels, a magnesium transmission casing and composite rear springs and load floor. This leaves the Ecostar a kerbweight of 1,406kg (around as% heavier than a normal Escort van) but it does retain the same loadspace.
There are six control modules in the Ecostar covering driver inputs, battery monitoring, converter control, diagnostic data logger, battery cooling, and battery heating system. A photo electric strip at the top of the windscreen powers a small fan in the bulkhead. If the temperature in the cabin reaches 27'C the fan cuts in to blow the hot air into the loadspace. This means the driver doesn't get into a hot cabin (and turn on the 4.5kW air conditioning unit fitted to US models). UK models have a diesel-fired cab heater operated by the normal heater controls.
Driving impressions
While the Ecostar may still be under development, it has a high build quality giving a 'together' feeling from the driving seat. In place of a rev counter there is a 'miles to discharge' meter, a percentage battery charge gauge and a fuel gauge for the diesel cab heater. There are four positions in the transmission: a single drive and reverse ratio plus neutral and park.
Turning the ignition key fully clockwise starts the motor (indicated by a green light on the dash). Once in gear the vehicle will creep (at 9km/h on flat ground) unless the foot or hand brake is applied Castor angles have been reduced to compensate for the loss of power-assisted steering. At manoeuvring speeds, the steering is still a little heavy but it lightens up nicely with speed. Low rolling resistance tyres help to reduce the required steering effort and extend the range.
When the vehicle is stationary the motor is in a stall but, like a steam engine, it produces maximum torque from zero revs. Given this, and the lack of gears to change, flooring the accelerator propels the vehicle to 48kin/h at a rate its internal combustion-engined sisters can't match (Ford quote an unladen 080km/h time of 12 seconds);
Noise levels are extremely low with only a muted whine accompanying our progress. The combination of high performance and low noise levels makes it all too easy to exceed speed limits.
There is no gauge to indicate
instantaneous battery drain but the miles to discharge meter is sensitive. When it hits zero (it is 10% pessimistic to allow for a reserve) the vehicle's acceleration and top speed are automatically limited to eke the maximum out of the remaining charge.
Ford has a vehicle of acceptable performance, range and payload, especially if it can get the price dividend down to its predicted 10%.
The company is working on options for financing the battery pack which should last for two years.